Recently, along with an advance of digital technology and improvement in data compressing technology, an optical disk such as a DVD (digital versatile disk) has been taking attention, and, an optical disk apparatus for reproducing information from such an optical disk has spread in the market along with a price reduction thereof.
An information amount of contents to process tends to increase year by year, and thereby, increase in a recording capacity in such an optical disk has been demanded. In order to increase the recording capacity of the optical disk, an optical disk having a plurality of recording layers and an apparatus for accessing such a type of optical disks have been developed eagerly.
As an optical disk having two recording layers provided only for reproducing information therefrom, a DVD-ROM (may be referred to as a ‘single-side double-layer DVD-ROM’ hereinafter) having two recording layers on one side has been put into a practical use. In this single-side double-layer DVD-ROM, information reproduction from each recording layer is achieved as a result of a laser beam being applied from one side and it being focused on a target layer. Accordingly, reproduction of information from each recording layer of the optical disk is allowed without turning over it. Further, as another type of an optical disk having two recording layers on which information can be recorded on one side, a DVD+R (may be referred to as a 'single-side double-layer DVD+R) exits. In this single-side double-layer DVD+R, also, reproduction of information from each recording layer without turning over the optical disk is allowed. Such a type of an optical disk having two recording layers on one side (referred to as a layer-0 and a layer-1) is generally referred to as a single-side double-layer disk, hereinafter.
In an information reproducing apparatus handling such a single-side double-layer disk, one of the following two scanning paths (referred to as a scanning path A and a scanning path B, respectively) is employed, as a scanning path for scanning with an optical spot from an address (current address) on one recording layer (referred to as X) to an address (target address) on another recording layer (referred to as Y). In the scanning path A, focus jump is carried out in a current position X from the recording layer X to the recording layer Y. Then, on the recording layer Y, seeking is carried out for the target address. In the scanning path B, an address on the recording layer X at the same radial position as that of the target address with respect to the optical disk radial direction is set as a temporary target address. Then, after seeking is carried out from the current address to the temporary target address, focus jump is carried out from the recording layer X to the recording layer Y (see Japanese Laid-open Patent Application No. 9-282675, for example). Generally speaking, since high speed scanning operation is easily achieved in the scanning path A than in the scanning path B, the scanning path A is employed in many information reproducing apparatuses handling single-side double-layer disks. It is noted that, Japanese Laid-open Patent Application No. 2002-8252 for example discloses a configuration in which focus jump and seeking are carried out in parallel.
In a single-side double-layer disk (for example, a single-side double-layer DVD+R before finalization), as shown in FIG. 16A, the entirety of a data zone of the layer 0 is an already-recorded zone, while, in the layer-1, a not-yet-recorded zone remains at a part (disk inner circumferential side) of the data zone, focus jump is carried out to the layer-1 in a position of an address ‘a’ as shown in FIG. 16B, in the above-mentioned scanning path A, for scanning with an optical spot from the address ‘a’ (current address) on the inner circumferential side of the layer-0 to an address ‘b’ (target address) of the already-recorded zone in the layer-1. However, in this case, since the layer-1 has the not-yet-recorded zone at the same position as that of the address ‘a’ with respect to a radial direction of the optical disk, address information otherwise included in reproduced data cannot be obtained, and thus, focus jump may not be carried out properly.
Further, as shown in FIG. 16C, when scanning with an optical spot from an address “a” (current address) to an address “b” (target address), first a temporary target address “a′” is set, and then seeking is carried out on the layer-1 to the temporary target address “a′”, in the scanning path B. However, since, in this case, the temporary target address is included in the not-yet-recorded zone, address information otherwise included in reproduced data cannot be obtained, and thus, seek error may occur.
Thus, in an information reproducing apparatus handling a single-side double-layer disk, information recorded at a target address may not be reproduced even when the target address is included in an already-recorded zone, for a case where a not-yet-recorded zone and the already-recorded zone are mixed in an optical disk.